U.S. patent number 4,362,060 [Application Number 06/195,108] was granted by the patent office on 1982-12-07 for displacement transducer.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Takashi Kugaya, Tsutomu Okayama.
United States Patent |
4,362,060 |
Okayama , et al. |
December 7, 1982 |
Displacement transducer
Abstract
A displacement transducer for measuring displacement brought
about by pressure, strain or the like comprises a sensor for
producing an electric signal representative of displacement, an
output amplifier for amplifying the signal output from the sensor,
an exciting circuit for exciting the sensor with a current or
voltage and adapted for controlling excitation in dependence on
deviation thereof from a reference value, and a correcting circuit
for correcting the excitation of the sensor thereby to correct
non-linearity of the output signal from the sensor. The correcting
circuit includes a first voltage divider circuitry of a fixed
dividing factor and a second voltage divider circuitry of a
variable dividing factor connected in parallel with the first
divider circuitry. The reference value is corrected by the voltage
dividing factor of the second divider circuitry thereby to correct
the excitation of the sensor. Correction of the non-linearity of
the output signals of negative and positive polarities can be made
with only a single correcting circuit.
Inventors: |
Okayama; Tsutomu (Katsuta,
JP), Kugaya; Takashi (Katsuta, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
14996636 |
Appl.
No.: |
06/195,108 |
Filed: |
October 8, 1980 |
Foreign Application Priority Data
|
|
|
|
|
Oct 8, 1979 [JP] |
|
|
54-128920 |
|
Current U.S.
Class: |
73/708; 73/721;
73/727; 73/862.623 |
Current CPC
Class: |
G01D
3/021 (20130101); G01R 15/005 (20130101); G01L
1/2275 (20130101) |
Current International
Class: |
G01L
1/22 (20060101); G01D 3/02 (20060101); G01R
15/00 (20060101); G01L 1/20 (20060101); G01L
009/06 (); G01L 019/04 () |
Field of
Search: |
;73/708,721,720,726,725,765,862.67,862.63 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Woodiel; Donald O.
Attorney, Agent or Firm: Antonelli, Terry and Wands
Claims
What is claimed is:
1. A displacement transducer for measuring displacement in a form
of an electric signal, comprising a sensor for producing an
electric signal in response to the displacement to be measured, an
output amplifier for amplifying the electric signal output from
said sensor, an exciting circuit for exciting said sensor with
current or voltage and controlling the magnitude of excitation in
accordance with deviation thereof from a reference value, and a
correcting circuit connected to the output side of said output
amplifier for correcting non-linearity of the output signal of said
sensor, said correcting circuit including a first voltage dividing
circuitry having a fixed voltage dividing factor and a second
voltage dividing circuitry having a variable voltage dividing
factor and connected in parallel to said first voltage dividing
circuitry, wherein a voltage dividing point of said first voltage
dividing circuitry is connected to a path for exciting said sensor,
while a voltage dividing point of said second voltage dividing
circuitry is connected to a circuit path for determining said
reference value.
2. A displacement transducer according to claim 1, wherein said
sensor includes pressure-sensitive elements connected in a bridge
circuit, while said exciting circuit includes a transistor
connected to said sensor for excitation with current and a
detecting resistor connected to said sensor for detecting the
exciting current, and an operational amplifier for controlling said
transistor in dependence on difference between said exciting
current detected by said detecting resistor and said reference
value.
3. A displacement transducer according to claim 2, wherein said
exciting circuit includes a voltage stabilizing element having one
end connected to an exciting current feeding terminal of said
sensor and the other end connected to the voltage dividing point of
the first voltage dividing circuitry of said correcting
circuit.
4. A displacement transducer according to claim 3, wherein said
transistor and said detecting resistor connected to said sensor are
disposed at the exciting current exit side of said sensor.
5. A displacement transducer according to claim 3, wherein said
transistor and said detecting resistor connected to said sensor are
disposed at the input side of said sensor for said exciting
current.
6. A displacement transducer according to claim 3, wherein said
transistor connected to said sensor is disposed at the exciting
current exit side of said sensor, while said detecting resistor is
disposed at the input side of said sensor for said exciting
current.
7. A displacement transducer according to claim 2, wherein said
exciting circuit includes a voltage stabilizing element having one
end connected to an exciting current feeding terminal of said
sensor and the other end connected to one of output terminals of
said output amplifier.
8. A displacement transducer according to claim 1, wherein said
sensor includes pressure-sensitive elements connected in a bridge
circuit, and said exciting circuit is arranged to supply a voltage
of said reference value as the exciting voltage to said sensor for
exciting it with voltage.
9. A displacement transducer according to claim 1, wherein said
correcting circuit is connected to said output amplifier and to
said exciting circuit for correcting the non-linearity of the
output signal of said output of said sensor of negative and
positive polarities.
10. A displacement transducer according to claim 1, wherein said
exciting circuit includes a voltage stabilizing element having one
terminal connected to a supplying terminal for supplying the
current or voltage to said sensor and having another terminal
connected to said correcting circuit.
11. A displacement transducer according to claim 10, wherein said
another terminal of said voltage stabilizing element is connected
to the voltage dividing point of said first voltage dividing
circuitry.
12. A displacement transducer for measuring displacement brought
about by pressure, strain or the like in a form of an electrical
signal which is then transmitted to a receiving side through a
two-wire type transmission line, including a receiving circuit
composed of a series connection of a d.c. power supply source and a
load resistor, and a measuring circuit connected to said receiving
circuit through the two-wire type transmission line,
said measuring circuit comprising an output amplifier constituting
a closed loop in cooperation with said receiving circuit and
adapted to convert a voltage signal to an amplified current signal
which is then output to said transmission line, a sensor including
pressure-sensitive elements connected in a bridge circuit and
adapted to produce an electrical signal in dependence on said
displacement, said electrical signal being applied to said output
amplifier, a constant-current circuit having one end connected to
one of output terminals of said output amplifier and the other end
connected to an exciting circuit adapted to control an exciting
current fed to said sensor, said exciting circuit including a
transistor and a detecting resistor connected to said sensor, said
resistor serving the detect the exciting current, a voltage
stabilizing element having one end connected to the other end of
said constant current circuit, voltage dividing means having one
end connected to one end of said voltage stabilizing element for
obtaining a reference value for the exciting current of said
sensor, and an operational amplifier for controlling said
transistor in accordance with deviation between said reference
value and a value detected by said detecting resistor, said
displacement transducer further comprising a correcting circuit
inserted between the other output terminal of said output amplifier
and one wire of said two-wire type transmission line for correcting
non-linearity of the output signal from said sensor, said
correcting circuit including a first voltage dividing circuitry
having a fixed voltage dividing factor and a second voltage
dividing circuitry having a variable voltage dividing factor and
connected in parallel with said first voltage dividing circuitry,
the voltage dividing point of said first voltage dividing circuitry
being connected to a path along which the current for exciting said
sensor flows, while the voltage dividing point of said second
voltage dividing circuitry is connected to the other end of said
voltage dividing means.
13. A displacement transducer according to claim 12, wherein the
other end of said voltage stabilizing element of said exciting
circuit is connected to the voltage dividing point of said first
voltage dividing circuitry.
14. A displacement transducer according to claim 12, wherein the
other end of said voltage stabilizing element of said exciting
circuit is connected to the other output terminal of said output
amplifier.
15. A displacement transducer for measuring displacement brought
about by pressure and strain in a form of an electrical signal
which is then transmitted to a receiving circuit through a two-wire
type transmission line, comprising a series connection of a d.c.
power supply source and a load resistor which constitute said
receiving circuit, and a measuring circuit;
said measuring circuit including an output amplifier forming a
closed loop in cooperation with said receiving circuit and serving
for converting a voltage signal into an amplified current signal to
be output to said transmission line, a sensor having pressure
sensitive elements connected in a bridge circuit and adapted to
produce an electrical signal representative of said displacement,
said electrical signal being applied to said output amplifier, a
constant-current circuit having one end connected to one of the
output terminals of said output amplifier and the other end
connected to an exciting circuit for controlling an exciting
voltage for said sensor, and a correcting circuit inserted between
the other output terminal of said output amplifier and a wire of
said two-wire type transmission line and serving to correct
non-linearity of the output signal from said sensor;
said exciting circuit including a voltage stabilizing element
having one end connected to the other end of said constant-current
circuit and the other end connected to said sensor at the exit side
of said exciting voltage, voltage dividing means having one end
connected to one end of said voltage stabilizing element for
obtaining a reference value for said exciting voltage, and an
operational amplifier for controlling said exciting voltage in
dependence on the output signal from said voltage dividing
means;
said correcting circuit including a first voltage dividing
circuitry having a fixed voltage dividing factor, and a second
voltage dividing circuitry having a variable voltage dividing
factor and connected in parallel with said first voltage dividing
circuitry, wherein a voltage dividing point of said first voltage
dividing circuitry connected to the other end of said voltage
stabilizing element, while a voltage dividing point of said second
voltage dividing circuitry is connected to the other end of said
voltage dividing means of said exciting circuit.
Description
The present invention relates in general to a displacement
transducer having a sensor adapted to respond to a mechanical
displacement brought about by stress, pressure or strain, for
example, and to produce an electric signal representative of the
displacement. More particularly, the invention concerns an
improvement on the displacement transducer in which the
nonlinearity of the electric signal outputted from the sensor is
corrected.
As a typical example of the sensor of the type stated above, there
is a semiconductor sensor. Among others, the semiconductor sensor
which is composed of a diaphragm of single crystal silicon having a
surface with pressure-sensitive elements such as diffused
monolithic gauge resistors is widely used. When the diaphragm of
the semiconductor sensor is subjected to mechanical displacement
due to stress, strain, distortion, or the like, the resistance
values of the pressure-sensitive elements undergo variation because
of the piezo-electric effect of the elements, whereby an electric
signal representing proportionately the mechanical displacement is
produced. As the displacement transducer incorporating the
semiconductor sensor, there can be mentioned a two-wire type
transmission circuit disclosed in U.S. Pat. No. 4,071,823. In the
following, the description is mainly directed to the two-wire type
transmission circuit.
The two-wire type transmission circuit is employed as the means for
measuring pressure or differential pressure in various
instrumentation systems and includes at the measuring side a sensor
for producing a voltage signal proportional to a pressure or
differential pressure to be measured, a constant-current circuit
for supplying an exciting circuit for exciting the sensor with
current or voltage and an output amplifier for amplifying the
voltage signal output from the sensor and converting the voltage
signal into a corresponding current signal which is then fed to a
two-wire transmission line. On the other hand, the receiving
circuit portion of the transmission circuit for receiving the
measurement signal from the measuring circuit described above
includes a series connection of a load resistor and a direct
current (d.c.) power source which is connected to the two-wire
transmission line.
The pressure-sensitive elements of the semi-conductor sensor are
connected in a bridge circuit. Consequently, when the
pressure-sensitive elements or the gauge resistor elements exhibit
a non-linear characteristic, a non-linearity (more precisely, a
signal component corresponding to a term proportional to a square
of the measured quantity) will appear in the produced voltage
signal as a function of variation in the quantity to be measured,
which eventually involves error in the measurement, since the
output signal from the semiconductor sensor is linearly amplified
by the output amplifier and transmitted to the receiving
circuitry.
An attempt for correcting the non-linearity of the output signal
from the semiconductor sensor is proposed in Japanese Laid-Open
Patent Application No. 149353/1978. According to the proposal, a
correcting circuit adapted to define a given correcting constant is
connected to the input of the output amplifier for determining a
correcting voltage on the basis of the given correcting constant
and the output signal from the semiconductor sensor, the correcting
voltage thus derived being applied to the semiconductor sensor.
However, this approach can correct the non-linearity of only one of
the measurement signals of positive and negative polarities.
Accordingly, two set of correcting circuits are required when the
positive and negative non-linearities of the measurement signal are
to be corrected.
An object of the present invention is to provide a displacement
transducer which is capable of correcting the non-linearity of
measurement signal of both negative and positive polarities with
the aid of a single correcting circuit.
According to an aspect of the invention, a correcting circuit is
constituted by a parallel connection of a first voltage divider
circuitry having a fixed voltage dividing factor and a second
voltage divider circuitry having a variable voltage dividing
factor. The correcting circuit is provided at the output side of an
output amplifier to thereby determine a reference value for
excitation voltage or current for exciting the sensor on the basis
of the output signal from the output amplifier, whereby the
excitation of the sensor is controlled to be equal to the reference
value. The reference value for the excitation is corrected by
adjusting the dividing factor or ratio of the second voltage
divider circuitry of the correcting circuit. With such circuit
arrangement, it is possible to perform continuously correction of
non-linearity of the measurement signal in both positive and
negative regions by using a single correcting circuit.
The above and other objects, features and advantages of the
invention will become more apparent from the following description
of the preferred exemplary embodiments of the invention. The
description makes reference to the drawings, in which:
FIG. 1 is a circuit diagram showing a displacement transducer for a
two-wire type pressure transmission circuit according to an
embodiment of the invention; and
FIGS. 2 to 5 show other exemplary embodiments of the displacement
transducer according to the invention.
Referring to FIG. 1 which shows an embodiment of the invention
applied to a two-wire type pressure transmitter, electric power for
the whole measuring circuit is supplied from a d.c. power supply
source 4 provided at the side of a receiving circuit through a load
resistor 6 and a transmission line.
In the measuring circuit portion, a constant-current circuit 5 is
provided to supply a constant current to a sensor 20, an exciting
circuit 25, a correcting circuit 24 and an output amplifier 1
independently from variation in voltage of the d.c. power supply
source 4 and variation in the voltage drop produced across the load
resistor 6.
The sensor 20 has a semiconductor strain gauge composed of a
diaphragm of single crystal silicon which has pressure-sensitive
elements R.sub.g1, R.sub.g2, R.sub.g3 and R.sub.g4 such as diffused
monolithic gauge resistor elements. The pressure-sensitive elements
R.sub.g1, . . . , R.sub.g4 are connected in a bridge circuit which
is excited by a current I.sub.S applied to the terminal c. A
voltage signal V.sub.o representing proportionately the pressure to
be measured makes appearance at output terminals b and d and is
supplied to the output amplifier 1.
The exciting circuit 25 is constituted by a Zener diode 21 serving
as a voltage stabilizing element for obtaining a constant voltage
V.sub.Z, a voltage divider circuit composed of resistor R.sub.1 and
R.sub.2 for obtaining a reference value V.sub.R for the exciting
current supplied to the sensor 20, a current detecting resistor
R.sub.3 for detecting a current I.sub.s flowing through the sensor
20, an operational amplifier 22 for controlling the exciting
current supplied to the sensor 20 in accordance with deviation of
the voltage V.sub.1 appearing across the detecting resistor R.sub.3
from the reference voltage V.sub.R (which is partially controlled
by the correcting circuit 24) derived from the voltage divider
resistor circuit (R.sub.1 ; R.sub.2), and a transistor 23 for
controlling the current I.sub.S flowing through the sensor 20 in
dependence on the output signal from the operational amplifier 22.
The transistor 23 and the current detecting resistor R.sub.3 are
connected to the sensor 20 at the exit side of the excitation
current. In this manner, the sensor 20 is excited by the current
I.sub.S which is in proportion to the reference voltage V.sub.R
determined by the exciting circuit 25 and the correcting circuit
24.
The correcting circuit 24 includes a first voltage divider
circuitry having a fixed division factor determined by fixed
resistor R.sub.o1 and R.sub.o2 and a second voltage divider
circuitry having a variable voltage division factor determined by a
variable resistor R.sub.X. The first and the second voltage divider
circuitries are connected in parallel to each other between
terminals e and f. The terminal e of the correcting circuit 24 is
connected to one of the output terminals of the output amplifier 1,
while the terminal f is connected to the receiving circuit portion
through a wire of a two-wire transmission line. The correcting
circuit 24 serves to correct the non-linearity of the output signal
from the output amplifier 1 by feeding back a part of the output
current I.sub.o of the output amplifier 1 to the exciting circuit
25. To this end, the fixed voltage dividing point of the first
voltage divider circuitry is connected to a junction between the
Zener diode 21 and the detecting resistor R.sub.3, while the
variable voltage tap point of the second divider circuitry R.sub.X
is connected to the resistor R.sub.2, whereby a voltage V.sub.f
proportional to the output voltage V.sub.o from the sensor 20 makes
appearance between the terminals e and f. By adjusting the driving
ratio of the second voltage divider circuitry to determine the
feedback ratio of the voltage V.sub.f to the reference voltage
V.sub.R, the non-linearity of the output signal from the sensor 20
is corrected.
By the way, the Zener diode 21 of the exciting circuit 25 serves to
stabilize those input signals which are supplied to the output
amplifier 1, the exciting circuit 25, the sensor 20 and the
correcting circuit 24, respectively, and additionally stabilize a
driving power source (not shown) for the operational amplifier 22
and the output amplifier 1.
The output current I.sub.o amplified and converted through the
output amplifier 1 from the output voltage of the sensor 20 which
voltage has been corrected in respect of the non-linearity through
operation of the correcting circuit 24 can be obtained from
terminals 7 and 8 of the receiving load resistor 6 which forms a
closed loop in cooperation with the output amplifier 1.
Next, correction of non-linearity performed by the circuit
arrangement shown in FIG. 1 will be elucidated in detail.
Taking into consideration the non-linearity of the pressure vis.
resistance characteristic of the pressure-sensitive elements
R.sub.g1, R.sub.g2, R.sub.g3 and R.sub.g4, the voltage V.sub.f
corresponding to the output voltage V.sub.o (unbalanced bridge
voltage) of the sensor 20 can be expressed in terms of a function
f(p) of pressure p and the exciting current I.sub.s for the sensor
20 as follows:
Further, the exciting circuit I.sub.s can be expressed in terms of
the exciting current detecting resistor R.sub.3 and the voltage
V.sub.1 appearing thereacross as follows:
In other words, the exciting current can be given by the following
expression: ##EQU1## where V.sub.z represents the Zener voltage of
the Zener diode 21, and x represents a variable which can be
determined continuously over both the positive and negative ranges
through settings of the variable resistor R.sub.x of the correcting
circuit 24. The variable x corresponds to the feedback ratio of the
voltage V.sub.f to the exciting current I.sub.s. The variable x is
zero, when the voltage divided by the fixed resistors R.sub.o1 and
R.sub.o2 is equal to the divided voltage tapped from a movable
terminal of the variable resistor R.sub.x. When the movable
terminal of the variable resistor R.sub.x is moved toward the
terminal e, the value of x is increased. On the other hand, when
the movable terminal is moved toward the terminal f, the value of x
is decreased.
Assuming, simply, that the current flowing the correcting circuit
24 is only the current I.sub.o from the output amplifier 1, and
current except the current I.sub.o is ignored, x is given as
follows: ##EQU2##
Where y is a dividing ratio of the second dividing circuit. When
the movable terminal is moved from the terminal e to the terminal
f, the y changes from 0 to 1.
From the expressions (1) and (3), the voltage V.sub.f which
corresponds to the output voltage V.sub.o (unbalanced bridge
voltage) from the sensor 20 can be expressed as follow: ##EQU3##
where I.sub.o represents the output current which is in proportion
to the voltage V.sub.f. As can be seen from the above expression
(4'), the term of f(p).sup.2 can be varied arbitrarily by varying
the value of x. The term f(p) comprises primarily terms p and
p.sup.2, wherein the term p.sup.2 is of a smaller value than that
of the term p. Accordingly, the term p.sup.2 included in f(p) can
be cancelled by the term xp.sup.2 which is a main term of
x.multidot.f(p).sup.2.
As can be seen from above examination of the expression (4'), the
relationship between the pressure p which is the quantity to be
measured and the output current I.sub.o which corresponds to the
output signal from the sensor 20 can be best approximated to a
straight line in a concerned pressure range by selecting the
variable x at the most appropriate value in the negative or
positive range through setting of the variable resistor R.sub.x of
the correcting circuit 24. In this connection, it is to be noted
that the variable x takes a positive value when the positive
non-linearity due to the negative value of the term p.sup.2 of f(p)
is to be corrected, while x takes a negative value for correction
of the negative non-linearity due to the positive value of the term
p.sup.2 of f(p). The value of x is zero, when no correction of the
non-linearity is required.
It will now be understood that the embodiment of the invention
described above allows the positive and negative non-linearities of
the output signal from the sensor to be corrected continuously in a
simplified manner by adjusting the single variable resistor element
R.sub.x of the correcting circuit 24.
FIG. 2 shows another preferred embodiment of the invention which
differs from the one shown in FIG. 1 in respect of the connection
of the correcting circuit 24. More specifically, in the case of the
circuit arrangement shown in FIG. 2, the connecting terminals of
the Zener diode 21 are connected to the output terminals of the
output amplifier 1 with a junction between the Zener diode 21 and
one output terminal of the output amplifier 1 being connected to
the terminal e of the correcting circuit 24, while the fixed
voltage dividing point of the first voltage divider circuitry is
connected to the exciting current detecting resistor R.sub.3. With
the circuit arrangement shown in FIG. 2, the range of positive
values taken by the variable x of the expression (3) can be
extended to thereby enlarge the range of the positive non-linearity
to be corrected, when the circuit parameters are selected identical
with those of the circuit shown in FIG. 1.
FIGS. 3 and 4 show further exemplary embodiments of the invention
which differs from the one shown in FIG. 1 in respect of locations
or positions of the current feeding terminal of the sensor 20 and
the excitation current detecting resistor R.sub.3 which take part
in the excitation of the sensor 20. In the case of the circuit
arrangements shown in FIGS. 3 and 4, the reference voltage V.sub.R
is shifted by a predetermined voltage level. In respect of the
means for generating the correcting term for the positive and
negative non-linearities, the circuit arrangements shown in FIGS. 3
and 4 are same as the one shown in FIG. 1.
In the case of the embodiments described above in conjunction with
FIGS. 1 to 4, the sensor 20 undergoes the current excitation by the
exciting circuit 25. However, arrangement may be made such that the
sensor 20 is voltage-excited, as is shown in FIG. 5.
Referring to this figure, the measuring circuit portion is
constituted by an output amplifier 1 which forms a closed loop with
the receiving circuit portion and serves to convert the voltage
signal into an amplified current signal to be delivered to the
transmission line, a sensor 20 having pressure-sensitive elements
connected in a bridge circuit and adapted to produce an electric
signal representing a displacement sensed by the pressure-sensitive
elements, the electrical signal output from the sensor 20 being
applied to the input of the output amplifier 1, a constant-current
circuit 5 having one end connected to one of the output terminals
of the output amplifier 1 and the other end connected to an
exciting circuit 25 to control the exciting voltage for the sensor
20, and a correcting circuit 24 connected between the other output
terminal of the output amplifier 1 and a wire of the two-wire
transmission line and adapted to correct the non-linearity of the
output signal from the sensor 20. The exciting circuit 25 comprises
a voltage stabilizing element 21 having one end connected to the
other end of the constant-current circuit 5 and the other end
connected to the sensor 20 at the outgoing side of the exciting
voltage, voltage dividing means composed of resistors R.sub.1 and
R.sub.2 and having one end connected to one end of the voltage
stabilizing element 21 for producing a reference value for the
exciting voltage, and an operational amplifier 22 for controlling
the exciting voltage in dependence on the output signal from the
voltage dividing means (R.sub.1 ; R.sub.2). On the other hand, the
correcting circuit 24 includes a first voltage dividing circuitry
composed of a series connection of resistors R.sub.01 and R.sub.02
having respective fixed resistance values, and a second voltage
dividing circuitry comprising a variable resistor R.sub.x so as to
exhibit variable voltage dividing ratio. The first and second
voltage dividing circuitries are connected in parallel with each
other. The divided voltage tap point of the first voltage dividing
circuitry is connected to the other end of the voltage stabilizing
element 21, while the divided voltage tap point of the second
voltage dividing circuitry is connected to the other end of the
voltage dividing means (R.sub.1 ; R.sub.2) of the exciting circuit
25.
In the foregoing description, it has been assumed that the sensor
is composed of pressure-sensitive elements connected in a bridge
circuit. However, the invention can be easily applied also to the
displacement transducer which makes use of a capacitance type
sensor.
In the case of the illustrated embodiments, the voltage V.sub.f
which is proportional to the sensor output signal is derived with
the aid of the output current circuit of the transmitter. However,
it will be a matter of design choice to utilize the output voltage
from the output amplifier directly as the voltage V.sub.f.
Thus, the circuit arrangement according to the invention can be
employed as a non-linearity correcting circuit in more general
sense to advantage.
Recently, many attempts have been made to reduce the non-linearity
of detector element in the field of the sensor technology. Under
the circumstances, the non-linear characteristic quantities tend to
be dispersed concentratively in the vicinity of zero in both the
negative and the positive regions. Thus, when the non-linearities
in both the negative and the positive regions can be corrected
continuously by means of one and the same circuit, not only the
correcting manipulation becomes much facilitated, but also the
circuit can be designed so that the absolute value of the
non-linearity of the detecting or sensor element itself is
minimized, whereby the magnitude of the quantity to be corrected
can be significantly reduced, involving eventually a remarkably
improved linearity after correction of the non-linearity in the
positive or negative region.
As will be appreciated from the foregoing, the invention has
proposed a displacement transducer whose non-linear characteristic
in the negative and positive regions of the output signal can be
corrected by using one and the same circuit of a simplified
construction, whereby the correcting manipulation or adjustment can
be efficiently carried out and at the same time the characteristic
of the sensor can be significantly improved.
* * * * *